Bench- and pilot-scale studies on the removal of pesticides from water by VUV/UV process

Abstract

As an advanced oxidation process, vacuum ultraviolet/ultraviolet (VUV/UV) process has recently gained increasing attention in water treatment, but assessment of its technical and economic feasibility for pesticide removal has rarely been conducted. This study investigated the degradation of five typical pesticides, including aldicarb (ALD), alachlor (ALA), chloroneb (CHL), methiocarb (MET) and atrazine (ATR), by VUV/UV under simulated water treatment conditions at both bench- and pilot-scales. Bench-scale tests showed that pesticide degradation followed pseudo-first-order kinetics and all pesticides were degraded by >90% at a VUV fluence of 12 mJ cm−2. The second-order reaction rate constants of ALD, ALA, CHL, MET and ATR with HO were 7.57 × 109, 4.89 × 109, 2.57 × 109, 3.81 × 109 and 2.38 × 109 M−1 s−1, respectively. Solution pH had varying influences on the degradation of different pesticides by VUV/UV. Inorganic anions (Cl−, NO3−, HCO3−) and natural organic matter (NOM) inhibited pesticide degradation by scavenging HO, but SO42− slightly promoted pesticide degradation. The toxicity of pesticide solutions was reduced by 33.7% to 74.8% after the VUV/UV treatment. In a long-term (80 d) operation of the pilot reaction system using a sand-filtered water, the stable performance with acceptable energy consumption (0.27–1.52 kWh m−3 Order−1) suggested a good application potential of the VUV/UV process for pesticide removal in small-scale water treatment.